Re: [PATCH] pci: Fixing drivers/pci/search.c compilation warning.

["Zhao, Yu" <yu.zhao@intel.com>]

Matthew Wilcox wrote:
> On Sun, Oct 26, 2008 at 08:51:25PM +0800, Yu Zhao wrote:
>> This reminds me of other problems of PCI search functions.
>>
>> The 'dev_start' is passed to bus_find_device(), and its 'knode_bus' 
>> reference count is decreased by klist_iter_init_node() in that function. 
>> The problem is the reference count may be already decrease to 0 because 
>> the PCI device 'from' is hot-plugged off (e.g., pci_remove_bus) when the 
>> search goes. A warning is fired when klist_iter_init_node() detects the 
>> reference count becomes 0.
>>
>> Some code uses pci_find_device() in a way that is not safe with the 
>> hotplug, because a device may be destroyed after bus_find_device() 
>> returns it and before it's held by pci_dev_get() in the next round. 
>> Following is an example from a random grep:
> 
> Yes, that's why pci_find_device() is deprecated.  But it doesn't also
> need to be buggy ;-)
> 

How about pci_get_bus_and_slot()? People would meet the problem with it 
anyway.

Thanks,
Yu